and thereby counteracting the vulnerability of cultivars with too narrow a genetic base to resist new races of pests and diseases.

IBPGR’s emphasis began to shift away from the collection of landraces as its work progressed and as plant breeding techniques advanced, and to include the wider gene pools of the crops such as the wild progenitors and close relatives. The materials conserved embrace an evolutionary spectrum of the past 10,000 years and include obsolete and fairly recent cultivars, but breeders’ lines rarely need conservation; their diversity is already present elsewhere. This point, which is not widely understood, has led pressure groups to urge the conservation of breeders’ lines, which except in a few cases is not justified. In any case, germplasm for major staple crops is available from the International Centres of the CGIAR, the parent body of IBPGR, and from several national agricultural research organizations.

For most of the major crops, germplasm collections provide opportunities for continued introduction of genes with conventional or sophisticated breeding techniques. For many minor crops that have not greatly diversified following domestication, collections may contain cultivars that may be introduced as crops to other countries without further breeding. Hence, the collections of the major crops, e.g., rice, wheat, millet, and groundnut, will be large, whereas those of the minor ones, e.g., okra, many tropical fruits, and forage crops, will be relatively small. As the value of such minor crops becomes appreciated, however, there is likely to be a need for a more diverse germplasm base.

The IBPGR budget is small (a little over U.S. $5 million per year); hence, it does not provide long-term institutional or program maintenance support but, rather, serves as a stimulus or catalyst to work done by national or international organizations. Some of its funds are used to carry out urgent work and to fill gaps in the collection. Linked with the IBPGR program are all crop genetic resources activities in the world, many collections of which were initiated and supported by IBPGR. IBPGR coordinates rather than directs these activities in which all participants are equal partners.

To date, IBPGR has organized more than 500 collecting missions in scores of countries. Germplasm has been acquired in accordance with established priorities (IBPGR, 1981; Williams, 1982) and conserved in long-term storage in 40 centers around the world. All major crops have now been placed in designated gene banks. The IBPGR is currently reviewing the financial support it gives to such gene banks and to centers that are actively involved in ensuring that genetic resources are available for use in crop improvement programs.

CROP ORIGINS AND GERMPLASM USE

Over the past few decades, a great deal of information has been accumulated on the origin and evolution of cultivated species. In general, the wild species tend to have limited patterns of distribution. Although Vavilov (1951) laid the basis for further work in defining centers of origin and centers of diversity based on observed botanical variation, the nuclear centers of the origin of agriculture have



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